One thing about the V brakes is the potential for using longer brake pads. V-brakes (meaning the mountain bike kind) use a much longer pad than a regular road bike. This should mean that the pad has much more surface area. This in turn should lead to cooler pad temps, significant on carbon rimmed wheels. I think it's Reynolds that has "special" pads for their carbon rims - one of the main features is that the pad is larger than a normal one. I may fiddle around with a V-brake pad for my regular sidepull brakes.

Although a rear V-brake really doesn't mean much in terms of anything aero, if it is lighter, uses bigger pads, and has no tire clearance issues (like sidepull brakes do) then they become a valid option.

Personally I like the look of the integrated brakes in the fork/frame but unfortunately for me I don't foresee such a frame in my future ever due to both cost and fit. I would commission an inexpensive custom frame that uses V-brakes if I saw a benefit to them, but the frames I order would only come with a normal fork.